1.2.6 Evaporative Cool Towers
Induce ventilation with humidity differentials: Evaporative cooling of hot and dry air at the tower’s top results in cooler, more humid and denser air that moves downward inside the tower, creating negative pressure at the tower’s top and positive pressure at the tower’s base. Air exiting the base supplies cooling and ventilation to occupied spaces.
Tower-chimney with mister at top, and strategic opening to spaces at the bottom, and water source or water pump.
The air flow in evaporative cool towers is humidity induced and occurs from the top to the bottom, thus in reverse direction of stack ventilation. Cool towers and stacks have been used separately; however, it is recommended that cool towers be used in conjunction with stack ventilation of the space in order to ensure stability of the air flow.
Cool towers provide a very low-cost ventilation strategy. Their effectiveness is ensured with a combination and building integration of stack ventilation. Some climates may allow cool towers to be used as a stack ventilator during the night.
Evaporative cooling and cool towers are most cost-effective in hot and arid climates.
Cool tower ventilation is only effective where outdoor humidity is very low and works best in hot and dry climates. A cool tower does consume water, a potential conflict in arid climates. Their effectiveness does not depend on wind, in fact wind speeds less than 7-10 mph are required to achieve significant cooling, allowing time for phase change. Cool towers work best with open floor plans due to air circulation unimpeded by walls or partitions.
1.2.5 Stack Ventilation
1.7.6 Nighttime Cooling
1.7.7 Evaporative Cooling